The present invention relates to a manufacturing method for a sealant-incorporated tire having an annular sealant chamber defined by an inner liner inside a tread, and relates also to a sealant-incorporated tire manufactured by this method.
A sealant-incorporated tire is known from Japanese Patent Application Laid-open No. 8-323875, for example. This sealant-incorporated tire has a sealant chamber at least a part of which is defined by an inner liner inside a tread of a tire body. The sealant chamber is filled with a sealant for sealing a puncture formed through the tread by a nail or the like to thereby delay air leakage from the puncture.
In manufacturing the above conventional sealant-incorporated tire, the inner liner is superposed onto the tire body prior to vulcanization. At this time, a mold release agent such as talc is preliminarily applied to a part of the contact surfaces of the inner liner and the tire body or to a part of the contact surfaces of inner liner elements forming the inner liner. In this condition, vulcanization is performed to integrate the inner liner with the tire body and form the sealant chamber by leaving the portion to which the mold release agent is applied unbonded.
It should be noted here that in performing vulcanization by inserting a green tire including a tire body and an inner liner into a heating die, the inner liner is expanded to produce an area where the density of talc as the mold release agent is high and an area where it is low. As a result, the boundary between a bonded portion and an unbonded portion of the inner liner in the vulcanization process is not clearly defined, so that there is a possibility that the shape of the resultant sealant chamber may become imperfect. Accordingly, there is a problem that it is difficult to form a sealant chamber having a desired shape, and the degree of freedom in designing the shape of the sealant chamber is limited.
The present invention has been accomplished with the above circumstances in view, and it is an object of the present invention to clearly define the boundary between the bonded portion and the unbonded portion of the inner liner in vulcanizing the green tire, thereby forming a sealant chamber having a proper shape.
To accomplish the above-described object, according to a first aspect and feature of the present invention, there is provided a sealant-incorporated tire manufacturing method comprising the steps of superposing an inner liner onto an inner surface of a tire body prior to vulcanization and bonding at least a part of the inner liner to the inner surface of the tire body by vulcanization to define an annular sealant chamber by the inner liner inside a tread of the tire body, in which a mold release sheet having a mold releasing property is placed on a portion of the inner liner facing to the sealant chamber prior to vulcanization.
With the above arrangement, the mold release sheet having the mold releasing property is placed on a portion of the inner liner facing to the sealant chamber in superposing the inner liner onto the inner surface of the tire body prior to vulcanization. Accordingly, this portion of the inner liner facing to the sealant chamber can reliably be prevented from being bonded by vulcanization to the inner surface of the tire body, and the remaining portion of the inner liner not facing to the sealant chamber can reliably be bonded by vulcanization to the inner surface of the tire body. As a result, the degree of freedom in designing the shape of the sealant chamber can be improved, and the sealant chamber can be formed into a proper shape.
According to a second aspect and feature of the present invention in addition to the above arrangement, there is provided a sealant-incorporated tire manufacturing method, wherein at least a part of one surface of the mold release sheet has the mold releasing property, and, in the vulcanization step, a part of the mold release sheet which has no mold releasing property is bonded to a wall surface of the sealant chamber by vulcanization.
With the above arrangement, the mold release sheet has a portion having the mold releasing property and a portion having no mold releasing property. The portion having the mold releasing property can prevent bonding of the inner liner to a part of the inner surface of the tire body by vulcanization to thereby form the sealant chamber. The portion having no mold releasing property allows the inner liner to be bonded to the wall surface of the sealant chamber by vulcanization to prevent random movement of the inner liner. Further, by setting the portion having the mold releasing property into a part of the one surface of the mold release sheet, the other part of the one surface can be used to bond the inner liner to the inner surface of the tire body by vulcanization, thereby stabilizing the shape of the sealant chamber.
According to a third aspect and feature of the present invention in addition to the first aspect and feature, there is provided a sealant-incorporated tire manufacturing method, in which the mold release sheet is formed of a material soluble in a sealant, so that the mold release sheet is dissolved into the sealant by injecting the sealant into the sealant chamber.
With the above arrangement, if the sealant is injected into the sealant chamber, the mold release sheet is dissolved into the sealant. Accordingly, a reduction in sealability of the sealant due to the presence of the mold release sheet in the sealant chamber can reliably be prevented.
According to a fourth aspect and feature of the present invention in addition to the third aspect and feature, there is provided a sealant-incorporated tire manufacturing method, in which the mold release sheet is formed of water-soluble paper or non-woven fabric.
With the above arrangement, the mold release sheet can reliably be dissolved into the sealant by injecting the sealant into the sealant chamber.
According to a fifth aspect and feature of the present invention in addition to the third aspect and feature, there is provided a sealant-incorporated tire manufacturing method, in which the mold release sheet is a film formed of a natural polysaccharide.
With the above arrangement, the mold release sheet can reliably be dissolved into the sealant by injecting the sealant into the sealant chamber.
According to a sixth aspect and feature of the present invention in addition to the first aspect and feature, there is provided a sealant-incorporated tire manufacturing method, in which a plurality of mold release sheets are laminated one on another.
With the above arrangement, even if the mold release sheets are expanded with the tire body and the inner liner in the vulcanization step, the contact surfaces of the plural mold release sheets mutually slide to thereby prevent breaking of the mold release sheets. Accordingly, undesired bonding of the tire body and the inner liner by vulcanization can reliably be avoided.
According to a seventh aspect and feature of the present invention in addition to the first aspect and feature, there is provided a sealant-incorporated tire manufacturing method, wherein the mold release sheet is folded into a corrugated shape prior to vulcanization, and the mold release sheet is expanded in the vulcanization step.
With the above arrangement, even if the mold release sheets are expanded with the tire body and the inner liner in the vulcanization step, the corrugated mold release sheet which is folded into a corrugated shape is freely expanded, so that it is prevented from being broken. Accordingly, undesired bonding of the tire body and the inner liner by vulcanization can reliably be avoided.
According to an eighth aspect and feature of the present invention, there is provided a sealant-incorporated tire which is manufactured by the sealant-incorporated tire manufacturing method according to any one of the first to seventh aspects and features.
With the above arrangement, it is possible to provide a high-quality sealant-incorporated tire having a sealant chamber proper in shape.